1. Field of the Invention
This invention relates to an amplifier circuit, specifically to an amplifier circuit to amplify a signal taken by a sampling transistor.
2. Description of the Related Art
An active matrix type LCD (Liquid Crystal Display) device and an organic EL (Electroluminescence) display device having an integrated drive circuit are previously known. This type of display device includes a pixel area in which pixels are arrayed in a matrix with m rows and n columns and the drive circuit disposed in its periphery. The display device is provided with a display voltage signal externally.
A wide range of the display voltage signal is used for the display device in order to enhance contrast of the LCD or brightness of organic EL elements. And a wide range of display signal output voltage is set in an external circuit (such as a peripheral LSI) of the display device to comply with such a requirement.
Required large display signal voltage described above is unfavorable to reduction in power consumption. Japanese Patent Application Publication No. 2000-81606, for example, describes a technology to reduce the power consumption which uses a driving method such as common inversion drive or sub-capacitor drive to reduce the display signal voltage and to reduce power supply voltage of the external drive circuit.
When applying the display voltage signal to the display device, it is necessary that an input load on the display device side, i.e. a display signal line for example, is driven enough. However, when the wide range of display voltage required for the display device is used as mentioned above, there is a problem that requirements of the wide voltage range and large driving capacity on the external circuit of the display device increase power consumption.